Tractor



March 17, 1936. E. E. wlcKl-:RsHAM 2,034,125

TRACTOR Filed oct- 2B, 1930 s sheets-sheet 1 March 17, 1936. E. E. wrcKERsl-IAM TRACTOR Filed oct. 2s, 19:504

6 Sheets-Shea?l 2 AT'T NEYs. f

March 17, 193s. E. E. WICK'ERSHAM y2,034,125

TRACTOR Filed oct. 2B, 1930 6 snee'ts-sneet 4 BY l 7 TIRNEYS/` 6 Sheets-Sheet 5 TRACTOR E. E. WICKERSHAM Filed Oct. 23, 1930 March 17, 1936.

mlmHfLh N March 17, 1936. E. E. wlcKl-:RSHAM TRACTOR Filed Oct. 25, 1950 '6 Sheets-Sheet 6 I A Tom/B1 Patented Mar. 17, 1936 TRA Elmer E. Wickersham,

CTR

San Leandro, Calif., as-

signor to Caterpillar-Tractor Co., San Leandro, Calif., a corporation of Californiav4 Application October 2B 27 Claims.

My invention relates to traction machinery and is particularly concerned with self propelled vehicles capable of operating over unprepared roadways. The device of my invention, although not limited thereto, is especially pertinent to tractors of the track laying type.

An object of my invention is to provide a tractor in which the major components are easily constructed as units and assembled together to provide a' complete mechanism.

Another object of my invention is to provide a tractor in which a large number of parts ordinarily considered necessary are dispensed with.

A further object of my invention is to provide a tractor which is extraordinarily accessible for assembly, repair and inspection.

The foregoing and other objects are attained in the embodiment of the invention shown in the drawings, in which Fig. 1 is a side elevation of a tractor-constructed in accordance with my invention, one of the forward idlers being removed. Y

Fig. 2 is a plan of the tractor shown in Fig. 1, certain portions being removed to increase the clarity of the disclosure.

vention comprises a body, generally tubular, providing a mounting for a source of power and being in telescopic relationship with a transmission unit housing in which a transmission unit is disposed. The tractor also comprises connections between the transmission unit and the source of power and connections between the transmission unit and ground engaging members mounted on the body.

In the f orm of my tractor which I have chosen to describe herein, there is provided a body 6 which preferably isI a tubular housing of cast metal. At a convenient point of its length, the body 6 is formed with a pair of oppositely disposed integral projections, such as outriggers I and 8, in which a stationary shaft 9 ls disposed. On opposite extremities of the shaft 9, crank arms I I and I2 are journalled. Since the crank arms are similar, a description of one of them will suce. The crank arm I2, for instance, isextended forwardly of the body 6 in the form of 1930, Serial No. 491,715

om. 1st- 9.2i

an I-beam and carriesv at its forward end a sliding journal block I3 through which an axle I4 passes. On opposite extremities of the axle, a pair of idlers I6 and I'I is mounted. In order to constrain the journal block I3 and, correspondingly, the idlers I6 and I'I, I provide a coil spring I8 which at one end abuts the journal block I3 and at the other end abuts a stationary stop I9I secured to the crank arm I2. By virtue of this spring mounting, the idlers I6 and I1 ordinarily are biased toward the forward end of the body 6 but can yield under a superior force.

To constrain the crank' arms II and I2 resiliently with respect to the body 6, there is provided a transverse leaf spring 2I spanning the crank arms II and I2 and mounted for frictional slidingmovement in guides 22 and 23 secured to the respective crank arms. Between its ends, the spring 2l is secured tothecentral portion of the tubular body 6. By virtue of this construction, the crank arms II and I2 are each mounted for movement with respect to the body 6; that is, for rotation about the axis of shaft 9. They' are, however, resiliently constrained and`move only under the urgency of a superior force.

In alignment with the idlers I6 and I1, but dlsposedadjacent the rearward portion of the body 6, are pairs of driving sprockets 26 and 21. Since the pairs of sprockets on opposite sides of the machine together with their appurtenant mechanism are substantially identical, I shall describe but one pair of them.. The sprocket 21 is preferably provided with an extended central hub 28 mounted onA anti-friction bearings 28 and 3l for free rotation on an axle casing 32 which is tubular in form and is removably joined at its inner end by fasteners such as studs to a boss 33 V forming part of the tubular body. 6. Mounted on the hub 28 is the sprocket 26 which is constrained to rotate therewith by a plurality of through bolts 34 which also secure for unitary rotation a V driving plate 36 carrying a hub cap 3l.l

Since my tractor is preferably of the track laying type, although not necessarily so, I prefer to connect the sprockets 26 and 2l and the idlers I6 and Il on each side of the body 6 with an endless chain or track 38 for engagement withl the ground. Although it is customary in tractors of the track layer'type to provide tracks which require external support, in this instance I prefer to use a self-supporting track which is flexible in one direction only and requires no external support. Such a self-supporting track is disclosed in the copending application of Clarence Leo Best, Serial Number 231,827, led November 8, 1927 and entitled Track link.

In a track of the type referred to, there are provided a plurality of similar,l interconnected links 39 each of which is pivoted to the succeeding link by a pivot -pin 4| and may be provided with a ground engaging projection 42. llach link preferably includes a centrally disposed upstanding lug 43 adapted to interengage with an upstanding loop 44 oi' the succeeding link In abutting relationship of the lugs 43' and the loops 44, the successive links are immovable for fiexure in one direction but are freely rotatable about the pivot pin 4| in the opposite direction. In accordance with this construction, a suitable ground engaging truck is provided at each side of the body 6 without the necessity for employing a complex, heavy truck frame as is ordinarily the case.

To render the tractor of my invention selfpropelling I provide it with a source of power. To this end the forward portion of the tubular body 6 is preferably formed with a laterally opening aperture` 5| through which a scource of power, such as an internal combustion engine 52, can extend. Preferably, the tubular body 6 is formed with an inturned ange 53 rimming the aperture 5I'and machined to provide a planar face against which the upper half 54 ofthe crank case of the internal combustion engine can abut. l The crank case half 54 provides a closure for the aperture 5| so that an oil-tight compartment 56 is formed by the upper half 54 of the crank case and the forward portion of the tubular body 6. The compartment 56 is preferably utilized as the crank chamber of the engine and in order to isolate'the crank chamber and to reinforce the body 6 I provide a forward bulkhead 51 comprising a wall integrally formed with the body 6 and disposed at the rear of the com.- partment 56.

The cylinder block 58 of the engine, including a plurality of cylinder barrels 59, is formed integrally with the upper crank case half 54 and carries an integrally formed or detachable cylinder head 6| in the customary fashion. Also integral with the upper crank case half 54 are bridge walls 62, 63 and 64 which respectively carry the rear main bearing 66, the center main bearing 61 and the front main bearing 68 -for the crank shaft 69 of the engine 52. Connecting the crank shaft 69 with pistons 1| operating in the cylinder barrels 59 are connecting rods 12.

At its forward end, the crank shaft 69 carries a nut 13 designed for co'operative engagement with a crankspindle 14 extending through the forward end of the tubular body 6 for attachment of a` hand crank thereto. The portion of the crank' case half 54 which overlies the spindle 14 forms a bracket 16 for the support of a cooling radiator 11.

Also attached to the forward end of the crank shaft 69 is a gear 18 which meshes with a timing gear 19 on a cam shaft 8| of the customary kind. In engagement with the timing gear 19 is a gear 82 journalled in a detachable housing 8 3 secured to the upper half 54 o f the crank case. Mounted on the shaft 84 is a pulley 85 carrying a belt 86 in engagement with a fan pulley 81. A fan shaft 88 journalled in a bracket 89 which is an extension` of .the housing 83 carries the pulley 81 and a cooling fan 9| in proper location with respect to the cooling radiator 11 Although not illustrated in detail, the engine is provided with an oiling system of a suitable ation of the lever |94.

sort and preferably employs the compartment I9 as an oil sump. I therefore prefer to form the body 6 with a. horizontally disposed baille 92 for providing an auxiliary sump 93. The rearward portion of the auxiliary sump 93 is contoured to allow for a seat 94 for the transverse spring 2|, previously described.

The rearward end of the crank shaft 69 carries a suitable ilywheel 96 operating in the com- .partment 56. Preferably formed as a unit with the ywheel is a master clutch 91 of any of the usual constructions provided with a clutch collar 98 for engaging and disengaging the clutch. For actuating the clutch 91, a fork 99 is in engagement with the clutch ycollar 98 and is pivoted as at |9| to the upper hall.l 54 of the crank case. 'I'he fork 99 projects through an aperture and is provided with an eye |92 for connection to a rod |93 extending to a'hand lever |94 pivoted as at |96 to the tubular body 6 vso that the clutch 91 can be engaged and disengaged by suitable'oper- In order to prevent the entry of dirt into the compartment 56 a flexible boot |91 preferably surrounds the fork 99.

Extending from the driven member of clutch 91 is a splined shaft |98 which terminates within a splined bearing, not shown, mounted in a sleeve |99 seated in a boss forming part of the bulkhead 51. The sleeve |99 is freely slidable in. the boss and is removably held in place by a set screw 2 accessible through an aperture ||3 in the body 6 ordinarily closed by a removable cover plate ||4. K

By virtue of the engine mounting on the tubular body 6, which has just been described, it is possible to remove the entire engine and clutch unit from the tractor without vseriously disturbing any of the other major units. In order to remove the engine 52 together with the fan 9| radiator 11 and their appurtenances and the clutch 91 and its appurtenances it is merely necessary to disconnect the rod |93 at the eye |92, remove the series of studs |'|6 which retain the upper halfv 54 of the crank case on the tubular body 6, remove the inspection plate ||4 and loosen the setV screw ||2. The collar sleeve |99 can then be translated axially for a suiilcient distance, to free the splined shaft |98. At the conclusion of these operations, the entire engine together with its crank shaft, ny wheel, clutch, fan and radiator can be lifted directly out of. the tubular body! leaving the laterallyopenin'g aperture 5|' therein exposed. With this type of construction, the removal of the engine for repair purmes or the quick insertion of a spare engine is a simple and expedient matter.

In order to transmit power from the engine 52 to the ground engaging members 38, I preferably employ a transmission unit generally designated ||1 which is mounted inatransmission unit -housing ||8. This housing is preferably of tubular form and is vusually constructed of Its outer diameter is such that it telescopes with in the open end of the tubular body 6 and is secured thereto by means of a flange ||9 on the ing running in the sleeve |09.

type. Mounted in a journal |29 provided by a boss in'the bulkhead |23 and in a. journal |3| provided by a boss forming part of a bridge .wall |32 of the transmission unit housing H8 is a main shaft |33. This shaft extends forwardly andis splined as at |34 to engage with the beary The splines |34 are preferably of such length that they permit the sleeve |09 to be retracted axially as previously described when it is desired to remove the engine unit.

The shaft |33 within the transmission unit housing ||8 is provided with a plurality of gears included in the change speed transmission. A slidable gear |36 is mounted on the shaft |33 for disposal in either one of two positions to afford second and reverse speeds for the tractor. Also mounted on the shaft |33 is a pair of gears |31 and |38 adapted to occupy either of two positions to aord low and high speeds for the tractor. The slidable gears |36, |31 and |38 are selectively translated by means of a shift lever |39 extending above the body 6 for convenient operation by the vehicle driver. The gear shift lever |39 is provided with a ball mounting |4| on a plate |42 secured to the tubular body 6 and extends through aligned apertures |43 and |44 in the tubular body 6 and in the transmission unit housing H8, respectively.

Also included in the change speed transmission are gears to mesh with the sliding gears previously described. Mounted on a shaft |46 which is journalled in a boss |41 in the bulkhead |23 and in a boss |48 in the bridge wall |32 are gears |49, |5| and |52. shaft |46 and are positioned to be engaged selectively by the sliding gears |38, |31 and |36, respectively. The reverse gear is not illustrated herein but is conventional.

At the rearward extremity of shaft |46, a bevel pinion |53 is provided to mesh with a bevel gear |54 carried in anti-friction bearings |56 and |51 mounted in webs |58 forming part of the transmission unit housing ||8. The bevel pinion |53 and the bevel gear |54 together constitute a bevel gear drive for transmitting power from the change speed transmission to a cross shaft |59. This shaft extends from the transmission unit housing ||8 through the apertured central portion of bosses |6| formed integrally therewith. In order to steer the tractor of my invention, I preferably incorporate steering clutches. Since these clutches are identical, simply being arranged in reverse order, I shall describe but one of them. At its outer extremity, the shaft |59 'is splined as at |62 tovcarry the driving spider |63 of a steering clutch generally designated |64.-

The spider |63 is'provided with an extension |66 journalledin a hushed boss- |61 formingpart of a cover plate |68 on a steering clutch housing |69 which is flanged as at |1| to be secured to the boss |6|. The driving clutch spider |63 is provided with external splines carrying a plurality of clutch plates |12 which are alternated with driven clutch plates. -A driven clutch spider |13 freely rotatable on' the extension|66 is normally urged by a plurality of springs |14 toward the driving clutch spider thereby compressing the alternated clutch plates for the transmission of power. The driven clutch plates are externally splined .to cooperate with internal splines on a clutch drum |16 which is an enlarged extremity of a sleeve |11 carried in an anti-friction bearing- |18 mounted in the clutch housing |69 and is separated from the shaft |69 by a bushing- |19.

The gears are iixed on the Due to the bias of springs |14 the clutch spiders are normally positioned to transmit power from the shaft |59 to the sleeve |11 and in order to disengage the clutch when desired,l I preferably provide on the driven clutch spider |13 a clutch collar |8| adapted to be axially translated by a fork |82 mounted on a vertical shaft |83 journalled in the steering clutch housing |69. A crank arm |64 on shaft |83 connects to a link |86 extending to a steering clutchy lever |81 in convenient reach of the vehicle operator. A corresponding steering clutch lever |88 connects by a link |89 to an operating crank |9| for the corresponding steering clutch on the opposite side of the machine. By suitable operation of the levers disengage the two steering clutches selectively.

I preferably augment the operation of the steering clutches for making especially sharp turns by brakes which also are effective to retard the motion of the tractor. Since a pair of similar brakes is used, one associated with each steering clutch, but one of them will be described.

Encompassing the drum 16 and disposed within the housing |69 is a brake band |92 adapted to be released or clamped in retarding position on the drum by means of an actuating rod |93 journalled in the clutch housing |69 and operated by a crank |94 which is connected through a rod |96 to a brake pedal |91. 'I'he corresponding brake, not shown, is operated by a pedal |98 connecting through a rod |99 to an operating crank 20|. By selectively operating the brake' pedals |91 and |98 the tractor operator can retard either or both of the driven drums of the two steering clutches and correspondingly control the tractor.

The driven sleeve |11 f one of the steering clutches terminates in a spur gear 202 while the driven sleeve 203 of the other steering clutch terminates in a spur gear 204. In order to obtain the desired speed reduction and in order to increase the ground clearance of the tractor by obviating the necessity of providing reduction gears having excessive pitch diameters, I prefer to incorporate in the transmission unit a speed reducing unit. To this end, spur gear 202 meshes with a gear 206 which revolves unitarily with a -pinion 201 mounted on a stub4 shaft 208 carried in an anti-friction bearing 209-mounted in the transmission unit housing ||8 and in. a.V bushing 2|| ldisposed in a central member 2|2 forming part of the transmission unit housing ||8. Correspondingly, the spur pinion 204 meshes with a gear 2|3 unitarily formed with a pinion 2|4 mounted on a stub shaft. 2|6 carried at one end in an anti-friction bearing 2 1 mounted in the transmission unit housing |I8 and at the other end seated in a bushing 2|8 disposed within the-member 2|2?4 VIn accordance with this construction, the gears 201 and 2|4 are capable of revolving independently or in unison depending |81 and |88, the tractor operator can engage and upon the operating condtion of the two steeringtending toldrive the sprocket wheels 26 and 21 at the other side of the tractor.

The described construction of the transmission unit and its housing is particularly advantageous in assembling the tractor at the factory and in subsequently disassembling for inspection or repair. In order to remove the entire transmission unit, it is but necessary to release the nuts on the bolts 34 and withdraw the driving plates 36 together with the axles 223 and 228 sufliciently to remove the splines from the quills 222 and 221. The ring of studs |22 can then be removed and after the disconnection of the various links and rods |86, |69, |96 and |99 the entire transmission unit housing `together with all of the mechanism mounted on it can be withdrawn from the rear open end f the tubular body 6. This unit is usually of such size that it can be placed upon a l component units of the tractor onto the tubular` bench convenient to the workman so that its initial construction and subsequent repair or inspection are greatly facilitated over present practice. Furthermore, after extraction of the transmission unit housing an entirely new unit can be reinstalled with the lapse of but a very few moments.

However, if it is not'desired to remove the entire transmission unit casing the cover plate |26 can easily be removed for inspection or adjustment of the exposed mechanisms. Alternatively the steering clutches together with their housings and appurtenant mechanisms can be detached either individually or together simply by removing the fastening means which secure the steering clutch housings |69 to the bosses |6| whereupon the splines |62 of the shaft |59 dis- -ing clutch or drive interrupting device, position saiddevice for ready accessibility for replacement or repair. Thus, the drive to and from the drive interrupting device is at the same side of the device, with one end of shaft |11 connected to the final drive means comprising gears 266, 261, etc., and with shaft |59 connected adjacent said end to the driving mechanism of the tractor. The steering clutches themselves thus form a bench 'assembly which facilitates greatly the production of the tractor and also inspection, repair or the replacement of the individual units in the eld within a very short space of time.

, Throughout the design and construction of my tractor, I have endeavored to make the various major units compact and easily removable from the tubular body 6 which forms the major support and framework of the machine. It is a matter of but a few moments to assemble the body 6 to provide a complete machine and furthermore it is a simple matter to remove from the tubular body 6 the individual components either singly or together in order to disassemble the tractor or to replace the individual units with v rality of forms.

ing members on said casings, and axles within said casings connected to said transmission unit and to said ground engaging members.

2. A tractor comprising a tubular body, an engine mounted on said body adjacent one end thereof, the crankshaft of said engine lying within said body, a transmission unit housing telescopically mounted within the other end of said body, a transmission unit in said housing, a shaft within said body connecting said transmission unit and said crankshaft, ground engaging members mounted on opposite sides of said body, and power transmitting means connecting said transmission unit and said ground engaging members.

3. A tractor comprising a tubular body having a laterally opening aperture adjacent one end thereof and being open at the other end thereof, an engine mounted on said body and projecting through said aperture, a transmission unit housing telescopically mounted within the o pen end of said body, a transmission unit in said housing, and a shaft within said body connecting said transmission unit and said engine;

4. A tractor comprising a tubular body open at one end and having a laterally opening aperture adjacent the other end thereof an engine mounted on said body and projecting through said aperture, the crankshaft of said' engine lying within said body; a tubular transmission unit housing, open at one end, telescopically mounted within the open end of said body to form a closure therefor; a trans ion unit in said housing; and a shaft within said body connecting said crankshaft and said transmission unit.

5. A tractor comprising a body open at one end;

a source of power mounted adjacent the other end of said body; a,y transmission unit housing, open at one end, telescopically mounted within the open end of said body and forming a closure therefor; a transmission unit mounted in said housing; and means for transmitting power from said source of power to said transmission unit.

6. A tractor comprising a body having a cylindrical opening at one end; a sourceof-power mounted on said body adjacent the other end thereof; a cylindrical transmission unit housing adapted to telescope said body opening to form a closure for said opening at said one end of said body; a transmission unit entirely supported on and disposed within said housng; and means for transmitting power from said source of power to said transmission unit.

7. A tractor comprising a body open at one end: a source of power mounted on said body adjacent the other end thereof; a transmission unit housing, open at one end, mounted on and telescoping said body to form a closure for said body; a cover plate closing the ,open end of said transmission unit housing: a transmission unitv in said housing and connected to said source of power; ground engaging members mounted on said body; and means connecting said transmission unit and said ground engaging members.

8. A tractor comprising a body, a source of power on said body, ground engaging members on said body, and a transmission unit telescoping one end of said body to engage said body for support and connected to said source of power and said ground engaging members.

9. A tractor comprising a body, a source of power on said body, ground engaging members on said body,- a transmission unit housing removably mounted on said body, and a transmission unit mounted on said housing, said transmission unit including a change-speed transmission connected to said source of power, a bevel gear drive connected to said transmission, and steering clutches connected to said bevel gear drive and to said ground engaging members.

10. lA tractor comprising aA body, a source of power on said body, ground engaging members on said body, a transmission unit housing on said body, a change-speed transmission on said housing and connected to said source of power, a bevel gear drive on said housing and connected to said transmission, clutch housings mounted on said transmission unit housing, steering clutches in said clutch housing and connected to said bevel gear drive, and means connecting said steering clutches and said ground engaging members.

l1. A tractor comprising a body, a source of power on said body, ground engaging members on said body, a transmission unit housing telescopically mounted on said body, clutch housings removably mounted on said transmission unit housing, means mounted in said transmission unit housing for transmitting power from said source of power to said ground engaging members, and

steering clutches interposed in said power transmitting means and mounted in said clutch housings.

12. A tractor comprising a, body, outriggers on said body, axle casings on said body, ground engaging trucks mounted on said axle casings and said outriggers, axles in said axle casings connected. to said trucks and extending into said body, a transmission unit housing on said body, a transmission unit in said transmission unit housing and connected to said axles, clutch housings on said transmission unit housing, clutches included in said transmission unit and disposed in said clutch housings, a source of power on said body, and means for connecting said source of power to said transmission unit.

13. A tractor comprising a body, a pair of axle casings projecting from opposite sides of said body, a pair of outriggers projecting from opposite sides of said body. crank arms on said outriggers, a spring spanning said crank arms and mounted on said body, a pair of ground engaging trucks` mounted on said crank 'arms and said axle casings, a source of power on said body, a transmission unit housing on said body, a transmission unit in said transmission unit housing, means connecting said source of power and said transmission unit, a pair of clutches included in said transmission unit, clutch housings encompassing saidclutches and mounted `on said .transmission unit housing, and axles within said axle casings and connected to said transmission unit andto said grolmd engaging trucks.

14. In a motor vehicle, a casing provided with an opening at one end, and a unitary structure including a transmission, wheels operable by said transmission, steering clutches for said wheels, and a housing for said transmission carrying said steering clutches, said housing being slidable onto and oi of said casing respectively to position said transmission and said clutches operatively and inoperatively with respect to said casing.

15. A.vehicle having a one-piece main frame substantially tubular in transverse cross section and having an opening in an end thereof, a first pair of wheels. members mounted on said frame to mount said pair of wheels rotatably, a transmission unit adapted to be unitarily positioned in said opening to operatively connect said pair of wheels to a source of power; a second pair of wheels, arms hinged on said main frame to support said second pair of wheels, and a self-sup porting chain passed about one of each of said pairs of wheels.

16. A vehicle having a one-piece main frame substantially tubular in transverse cross section and having an opening in an end thereof, a rst pair of wheels, members mounted on said frame to mount said pair of wheels rotatably, a transmission unit adapted. to be telescoped into said opening to operatively connect said pair of wheels to a source of power, a second pair of wheels, arms hinged on said main frame to support said second pair of wheels, and a self -supporting chain passed about one of each of said pairs of wheels.

1'7. In combination aoasing, a wall in said casing, a drive member .journalled in said-wall, a transmission unit, a housing for said unit adapted to telescope said casing and extend toward said wall, said housing including a bulkhead positioned adjacent said wall when said housing telescopes said casing, and a driven shaft journalled in said bulkhead and engaged with said drive member for rotation. l

18. I'n a tractor, a rigid main frame including a transmission case, ground-engaging members supported by said main frame, `a power plant, a transmission, a transmission frame upon which said transmission is supported as a unit, said transmission case of said main frame having an opening through which said transmission frame with the transmission supported thereon is insertable and removable as a unit, said transmission including speed change mechanismand a shaft for connection with said power plant, and steering devices for said ground-engaging members, said steering devices being supported by said transmission frame for positioning therewith and being connected with said transmission.

19. In a track-type tractor, a rigidv main frame including a transmission case, a track mechanism at each side of said main frame and supported thereby, a power plant, a transmission, a transmission frame upon which said transmission is supported as a unit, said transmission case of said main frame having an opening in the rear end through which said transmission frame with the transmission supported thereon is insertable `and removable as a unit, said transmission frame having a portion projecting beyond the rear end of said transmission case when said transmission frame is in position in said transmission case,

' said transmission including speed change mechanism and a shaft for connection with said power plant, and steering devices for said track mechanisms, said steering Adevices being supported byv said transmission is supported as a unit, said transmission case of said main frame having an Uli sion frame is in position in said transmission case, and steering devices for said ground-engaging members, said steering devices being supported by the projecting portion of said transmission frame transmission.

21. In a track-type tractor, a main frame including a transmission case, a power plant, track mechanisms supported by said main frame, a transmission, a transmission frame upon which said transmission is supported as a unit, said transmission case of said main frame having an opening through which said transmission frame with the transmission supported thereon is in- Vand being connected with said sertable and removable as a unit, said transmission including speed change mechanism and a shaft for'connection with said power plant, and steering devices for said track mechanisms, said steering devices being supported by said transmission case adjacent the rear end thereof for ready accessibility and being connected with said transmission. j

22. In a track-type tractor, amain frame including a transmission case, a power plant.' track mechanisms supported by' said main frame, a transmission, a transmission frame moon which said transmission is'supported as a unit,- said transmission case of said main frame having an opening through which said transmission frame with the transmission supported thereon is insertable and removable as a unit, said tansmis- A drive shaft projecting through said transmission case and detachably connected with said transmission unita driving wheel means for supporting said driving wheel by said transmission case outside therof for rotation about the axis of said drive shaft. said supporting means being inde-I pendentof said driving shaft, anddetachable means connecting said shaft and said wheel, whereby the transmission unit can be removed by detaching said detachable means and moving said Shaft to break the connection between said shaft and said transmission unit.

24. In a motor vehicle, a main frame including a transmission case. a transmission'removably mounted in said transmission case as a unit and without dismantling of said main frame, a drive shaftfprojectng through said transmission `case and detachably connected with said transmission unit, tubular supporting means connected to said transmission case outside thereof and through which said drive shaft projects, a driving wheel outside of said transmission case and supported for rotation on said tubular supporting means independent of said drive shaft, and de- 5 tachable means connecting said shaft and said wheel, whereby the transmission unit can be removed by detaching said detachable means and movingsaid shaft to break the connection between said shaft and said transmission unit. 1

25. I n a motor vehicle; a main frame including a transmission case, ground-engaging members supported by said main frame, a transmission, a transmission frame upon which said transmission is supported as a unit, said transmission case of 1 said main frame having an opening through which said transmission frame with the transmission thereon is insertable and removable as a unit, and steering devices for said groundengaging members and supported by said trans- 2 mission frame outside of said transmission case; each steering device being connected with said transmission by a shaft extending outwardly from said transmission frame, and'means including a tubular shaft about said first-mentioned 2 shaft connecting said steering device with a ground-engaging member.

26. a tractor comprising a body, a source of power on said body, spaced ground-engaging means connected to said body, a transmission v unit frame removably supported by said body and telescopically insertable and removable through an aperture in said body, a transmission unit ,supported by said frame-for removal therewith and including a change-speed transmission con- 3 'nected to said source of power; and means for driving each of said ground-engaging means from said change-speed transmission including a drive interrupting device, a tubular shaft connected to said device, and a -shaft connected to said de- 4 vice and extending through said tubular shaft, said tubular shaft and said shaft providing means for positioning saiddevice for ready accessibility. 27. A tractor comprising a body, a source of power on said body, spaced ground-engaging means connected to said body, a transmission unit frame removably supported by said body and telescopically insertable and removable through an aperture in said'body, a transmission unitsupported by said frame for removal therewith 5 and including achange-speed transmission connected to said source of power;Y and means for driving eachv of said ground-engaging means from said change-speed transmission including a drive interrupting device having driving and .55

driven elements, a shaft connected to one of said elements, and a tubular shaft connected to the other of said elements and journalled-for rotation about said shaft. 

